Treatment of Hypothyroidism

Abstract

Hypothyroidism is currently a condition that can be treated, but not cured. The first routinely used thyroid hormone replacement was desiccated thyroid extract. Synthetic levothyroxine, which replaces thyroxine and relies on its peripheral conversion to the active hormone triiodothyronine, has since become standard. Levothyroxine is a well-tolerated therapy for hypothyroidism. There is a robust body of data concerning its benefits and a long duration of experience with its efficacy in reversing the symptoms of hypothyroidism. It is considered the standard of care for multiple reasons, including the fact that it is easy to administer, is an inexpensive medication, has good intestinal absorption, shows a favorable side effect profile, and has a long serum half-life. Although levothyroxine reverses most stigmata of hypothyroidism in the majority of individuals, some patients feel dissatisfied with “monotherapy.” This has stimulated interest in “combination therapy” with both levothyroxine and liothyronine. Trials of combination therapy have generally not shown benefit, although some patient preference for combination therapy exists. It is possible that the trials conducted thus far have not selected the appropriate outcome measures or targeted the appropriate populations. Monotherapy and combination therapy each carry their particular risks and safety concerns, chiefly nonphysiologic hormone ratios and inadvertent thyrotoxicosis. Research regarding which therapy fully reverses hypothyroidism at a tissue and cellular level is ongoing. In the future, regeneration of functional thyroid follicles from stem cells may offer hope for curing hypothyroidism.

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